If you are looking for a cool and free psd mockup of a Surface ,this freebie may help you.
Mockup Freebie psd created and released by Deani Hansen (Titter,Facebook,LinkedIn)
License info: According to Deani Hansen,the author of this freebie,it’s licensed under Attribution-ShareAlike 3.0 Unported.

Surface Pro 3 Mockup

You can download this free mockup psd file from here: Download PSD